class Solution{
    public List<Integer> findSubstring(String s, String[] words){
        List<Integer> ret = new ArrayList<Integer>();
        Map<String,Integer> hash1=new HashMap<String,Integer>();
        for(String str:words) hash1.put(str,hash1.getOrDefault(str,0)+1);
        int len=words[0].length(),m=words.length;
        for(int i=0;i<len;i++){
            Map<String,Integer> hash2=new HashMap<String,Integer>();
            for(int left=i,right=i,count=0;right+len<=s.length();right+=len){
                String in=s.substring(right,right+len);
                hash2.put(in,hash2.getOrDefault(in,0)+1);
                if(hash2.get(in)<=hash1.getOrDefault(in,0)) count++;
                if(right-left+1>m*len){
                    String out=s.substring(left,left+len);
                    if(hash2.get(out)<=hash1.getOrDefault(out,0)) count--;
                    hash2.put(out,hash2.get(out)-1);
                    left+=len;
                }
                if(count==m) ret.add(left);
            } 
        } 
        return ret;
    }
}